PowerPoint Slideshow about 'Definition of Terms' - barny

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The polygraph is used to test or question individuals for the purpose of detecting deception or verifying truth of statements through a visual, permanent and simultaneous recording of a person’s cardiovascular and respiratory pattern as a minimum instrumentation requirement.

Within the U.S. federal government, a polygraph examination is also referred to as a PSYCHOPHYSIOLOGICAL DETECTION OF DECEPTION (PDD) examination. Several other technologies are also used in the field of lie detection, but the polygraph is the most famous.

The idea that lying produces physical side-effects has long been claimed. In West Africa persons suspected of a crime were made to pass a bird's egg to one another. If a person broke the egg, then he or she was considered guilty, based on the idea that their nervousness was to blame. In ancient China the suspect held a handful of rice in his or her mouth during a prosecutor's speech. Since salivation was believed to cease at times of emotional anxiety, the person was considered guilty if by the end of that speech the rice was dry.

Cesare Lombroso, an Italian scientist, employed the first scientific instrument to detect deception – HYDROSPHYMOGRAPH, measured changes in pulse and blood pressure when suspects were questioned about their involvement of a specific offense.

A device recording both blood-pressure and galvanic skin response was invented in 1920 by Dr. John A. Larson of the University of California and first applied in law enforcement work by the Berkeley Police Department under its nationally renowned police chief August Vollmer

It is the alteration of consciousness and concentration in which the subject manifests a heightened of suggestibility while awareness is maintained.

Not all persons are susceptible to hypnotic induction. Subjects who are compulsive-depressive type, strong-willed like lawyers, accountants, physicians and other professionals are usually non-hypnotizable.

Fidgeting – subject is constantly moving about in the chair, pulling his ears, rubbing his face, picking and tweaking the nose, crossing or uncrossing the legs, rubbing the hair, eyes, eyebrows, biting or snapping of fingernails. These are indicators of nervous tension.

Swearing to the truthfulness of his assertion – usually a guilty subject frequently utters such expression. “I swear to God I am telling the truth” or “ I hope my mother drops dead if I am lying”, “I swear to Go”…etc. Such expressions are make to make forceful and convincing his assertion of innocence.

Inability to look at the investigator “straight in the eye” – the subject does not like to look at the investigator for fear that his guilt may seen in his eyes. He will rather look at the floor or ceiling.

A noble lie is one that would normally cause discord it if were uncovered, but that offers some benefit to the liar and perhaps assist in an orderly society and thus potentially gives some benefit to others also.

It is often told to maintain law, order and safety.

A noble lie usually has the effect of helping an elite maintain power.

Pretending to have capability or intention one doesn’t. Bluffing is an act of deception that is not usually seen as immoral because it takes place in the context of a game where this kind of deception is consented to in advance by the players.

The polygraph instrument usually measures four to six physiological reactions recorded by three different medical instruments that are combined in one machine. Older polygraph machines were equipped with long strips of paper that moved slowly beneath pens that recorded the various physiological responses. Newer equipment uses transducers to convert the information to digital signals that can be stored on computers and analyzed using sophisticated mathematical algorithms.

Blood pressure and heart rate are measured by the cardio-sphygmograph component of the polygraph, which consists of a blood pressure cuff that is wrapped around the subject's arm.

During the questioning the cuff remains inflated.

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The movement of blood through the subject's veins generates a sound that is transmitted through the air in the cuff to a bellows that amplifies the sound. The magnitude of the sound relates to the blood pressure and the frequency of the changes in the sound relates to the heart rate.

The pneumograph component of the polygraph records the subject's respiratory rate. One tube is placed around the subject's chest and a second is placed around his or her abdomen. These tubes are filled with air. When the subject breaths, changes in the air pressure in the tubes are recorded on the polygraph.

It consists of electrical sensors called galvanometers that are attached to the subject's fingertips. The skin of the fingertips contains a high density of sweat glands, making them a good location to measure perspiration.

question2. Irrelevant Question - 3. Relevant Question - In a polygraph test, the types of questions alternates, the test is passed if the physiological responses during the probable lie control questions are larger than those during the relevant question.

1. Pre-Test Phase - the examiner discusses with the subject the test issue, review the test questions that will be ask during the test and assess the subjects emotional and physiological suitability to undergo the polygraph test.2. Testing Phase - subjects physiological responses are recorded as the subject answers a set of questions reviewed earlier.3. Post Test Phase - examiner reviews test data obtained and interprets the polygraph chart.

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* A polygraph test normally lasts between one and a half hours to two and a half hours.* Polygraph test result in the philippines is not admissible in evidence as proof of the guilt of an accused.* Polygraph test is voluntary.* The accuracy of polygraph test is about 90% provided the examiner is competent and the polygraph machine is in good working condition.* Polygraph is an investigative tool.* The principle behind a lie detection test is that when the subject hears a questions which he or she intends to lie, the brain interprets and triggers automatic and uncontrollable physiological changes captured by the polygraph.

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Who Uses The Polygraph1. Law Enforcement Agencies2. Legal Community3. Private SectorKinds of Errors in a Polygraph Test1. False Positive - occurs when a truthful examinee is reported as being deceptive.2. False Negative - when a deceptive examinee is reported as truthful.Causes of Polygraph Errors1. Failure of examiner to properly prepare the examinee for the examination.2. Misreading of the physiological data on the polygraph charts.3. Defective polygraph machine.